Combination locks have been used in conjunction with deadbolt locks and are particularly useful in environments whenever the high security of a room requires not only that an individual can operate the combination lock from the exterior of the room in order to gain entry but also to exit the room by merely withdrawing the deadbolt lock should the combination lock have been inadvertently or deliberately returned to its locked or secured position.
An example of a deadbolt mechanism which incorporates or is used with a combination lock is the Model 8470 Deadbolt manufactured by Sargent and Greenleaf Company of Nicholasville, Ky. The combination lock which has previously been adapted for use with and is predominantly used with the Sargent and Greenleaf 8470 deadbolt is the Sargent and Greenleaf Model 8470. Such an assembly is illustrated in FIG. 5 of U.S. Pat. No. 4,961,330 to Walter R. Evans, entitled "High Security Panic Exit System." Also available and substantially the same is the Lockmasters LM5100 deadbolt which may accommodate a number of combination locks similar to the Sargent and Greenleaf combination lock. The Lockmasters device is available from Lockmasters, Inc. of Nicholasville, Ky. The Lockmasters LM5100 Deadbolt which may be used with any of several combination locks such as the Sargent and Greenleaf Model 8470 is illustrated in U.S. Pat. No. 5,257,519.
In order to operate the combination of a combination lock and the deadbolt lock mechanism and to permit the deadbolt to be withdrawn while the combination lock bolt will remain in an extended or locked position and then to permit the deadbolt to be extended into its locked position, the two bolts typically are connected by a lost motion connection.
The lost motion connection between the two bolts permits the combination lock bolt to pull the deadbolt to a retracted position and still permits the combination lock bolt to be extended into its locked position without positively forcing the deadbolt to extend. This arrangement also permits the operation of the combination lock for withdrawal of its bolt to cause the withdrawal of the deadbolt while also permitting the deadbolt to be retracted in order to exit the secure room even though the combination lock bolt remains in its locked or secure condition.
The Mas-Hamilton Group X-07 Electronic Combination Lock, an electronic combination lock available from Mas-Hamilton Group, Lexington, Ky., has a magnetic anti-attack interlock incorporated into the frame and bolt of the lock, as described in U.S. Pat. No. 5,271,253 entitled, "Electronic Combination Lock With Magnetic Anti-Attack Interlock," and issued to Thomas E. Cassada, et al.
The interconnection of both the referred Sargent and Greenleaf lock and the Sargent and Greenleaf deadbolt incorporates a T-shaped extension on the deadbolt and an opposing flange or lip formation on the combination lock bolt to pull the deadbolt. A sufficient relief is present within the combination lock bolt to permit the combination lock bolt to extend while the deadbolt is retained in a withdrawn position. This relief, relatively large in size, does not permit the continued incorporation of the magnetic interlock described in U.S. Pat. No. 5,271,253, because the position of the magnetic interlock extends into the relief and potentially interferes with the T-shaped head of the deadbolt whenever the deadbolt is retracted and the combination lock bolt is extended. For optimum security, the magnetic anti-attack interlock is required; and, therefore, alternative interconnection approaches are necessary.